The present invention relates generally to a bicycle, and more particularly to a dual dial rods speed changing controller of the bicycle, which is capable of linear displacement.
As shown in FIG. 1, a prior art dual dial rods speed changing controller comprises a rotary wire hub seat 1 and a ratchet wheel 2, which are mounted coaxially on a pivot 4 of a base 3 and are fastened together. The wire hub seat 1 is of a round tray like construction and is fastened at one end with a guide wire 5 of the speed changing controller such that the center of the guide wire 5 and the axial center of the pivot 4 are separated by a constant distance r (rotational radius). The advancing dial rod 6 or the withdrawing dial rod 7 is dialed to control the gear change, the ratchet pawl 8 (or ratchet pawl 9) is engaged with a tooth of the ratchet 2, so as to actuate the ratchet 2 to turn. The ratchet 2 actuates the wire hub seat 1 to turn so as to cause the guide wire 5 to pull on the axial center of the pivot 4 serving as a center, thereby resulting in the control of speed change.
The prior art structure described has the following deficiencies.
The precision gear location of the prior art speed changing controller has to do with the magnitude of an interval between the adjoining ratchet teeth and the distance r between the center of the guide wire and the axial center of the pivot 4. The magnitude of the interval of the adjoining ratchet teeth determines the revolving angle of the ratchet 2. Generally speaking, the tooth distance of the ratchet of the same controller and the magnitude of the guide wire diameter are attained by calculation. Their relationship is fixed. The guide wire 5 is vulnerable to detachment from the wire hub seat 1 due to the constant drag. As a result, the guide wire must be replaced with a new one which must be equal in diameter to the old one. If the new guide wire is greater or smaller in diameter than the old guide wire which is replaced, there will be a change in the distance between the center of the guide wire and the axial center of the pivot. As a result, the specified tensile of the guide wire may turn out to be excessive or inadequate, thereby undermining the efficiency of speed change control.
The guide wire is made of a steel filament having a specified rigidity. As the guide wire is wound on the wire hub seat, the guide wire is not in an intimate contact with the rotary wall surface of the wire hub seat due to the insufficient pull force. As a result, there will be a change in the distance between the center of the guide wire and the axial center of the pivot.
The primary objective of the present invention is to provide a dual dial rods speed changing controller capable of linear displacement and suitable for use in conjunction with guide wires of various diameters.
The primary objective of the present invention is to provide a dual dial rods speed changing controller capable of linear displacement and suitable for use in conjunction with the guide wires of various diameters.
The controller of the present invention is intended to bring about the action of dragging the guide wire of a speed changer. The controller comprises a base; a wire hub seat mounted on the base such that the wire hub seat moves linearly in a reciprocating manner and that the wire hub seat is fastened at one end with the guide wire; an advancing member mounted on the base and provided with an advancing dial rod capable of swiveling between a first position and a second position so as to actuate the wire hub seat to advance at the time when the advancing dial rod is acted on by an external force. When the advancing dial rod is relieved of the external force, the advancing dial rod swivels back to the first position; a withdrawing member mounted on the base and provided with a withdrawing dial rod capable of swiveling between a third position and a fourth position at the time when the withdrawing dial rod is exerted on by another external force, thereby linking the wire hub seat to displace in reverse. As the withdrawing dial rod is relieved of the external force, the withdrawing dial rod swivels back to the third position.